Dehumidifying apparatus



Oct. 21, 1958 G. A. KELLEY ETAL DEHUMIDIFYING APPARATUS Filed Oct. 20,1955 INVENTORS, G. A. KELLEY,

BY H. E. PARKER DEHUMIDIFYING APPARATUS Gilbert A. Kelley, Toledo, Ohio,and Herbert E. Parker,

Application October 20, 1955, Serial No. 541,743

6 Claims. c1. 1832) This invention pertains to controls forabsorption-type dehumidifying apparatus and has particular adaptabilityto such apparatus used in shipboard operation.

Dehumidification in air conditioning has been applied to numeroussituations since its inception. A recent example of this has been todehumidify the holds of ships transporting items that are damageable bymoisture. A particular application is in the transportation of steelthrough sea water of varying temperature such as from the East Coastthrough the Panama Canal to the -West Coast where sea water temperaturesmay vary from 40 F. to 90 F. during the voyage. When this sea water isused as a cooling medium in the dehumidification apparatus, thetemperature of the cooling coils, air, and hygroscopic solution thereinwill be correspondingly changed; Such a change results in variousoperating problems in the dehumidification apparatus as will beamplified later.

It is an object of our invention to provide dehumidifying apparatus andcontrols therefor that will efficiently operate at all temperatures ofsea water that a ship may encounter.

For'further consideration of what we believe novel and our inventionrefer to the drawing and following specification.

In the drawing:

nits States Patent Figure 1 is a partially schematic view ofdehumidifying apparatus embodying our invention,

Figure 2 shows a detail of Figure 1, and

Figure 3 depicts alternate controls that may be used with the apparatusof Figure 1.

The unit comprises a washer casing 11, a regenerator casing 12, and asump 13. Bulkhead 21 is a portion of the hull of the ship and a deck 22is provided on which the apparatus rests. Fresh air, or air from thehold to be dehumidified, is drawn through duct 14, and passed by coolingcoils 15 and spray 16 by blower 17. This is delivered to the holdthrough duct 18. In contactor or washer casing 11, the air isdehumidified by means of the spray 16 which is a hygroscopic solution,such as lithium chloride in water, emitting from nozzles in spray bar 20and draining to sump 13. The air is also cooled by coils 15, which havesea water passing therethrough.

Solution is supplied to spray bar 20 by means of pump 23 which alsosupplies a relatively small amount to spray bar 24, the amounts beingproportioned by orifices 25 and 26. 1 Spray 27 from spray bar 24 flowsover heating coils 28 and hence back to'sump 13. Scavenger air from theoutside atmosphere, contacted with spray 27, enters duct 30 and exhauststhrough pipe 32 by means of blower 31. This air is generally ducted froman outside air source and is used to carry oif water which is expelledwhen the solution 'is heated by the coils 28 through which a heatingmedium such as steam is passed. The flow of the heating medium iscontrolled by a pneumatically operated valve 33.

Flowof sea water through coil 15 is maintained at a constant, full rateby pump 19 under all conditions.

This enables maximum cooling and maximum dehumidification since thehygroscopic solution is more efiective at lower temperatures. A largevariation in sea water temperature is generally encountered in thevoyage of a ship and consequently produces a large temperature variationin cooling coils 15. However, the cooling coils will still be at thelowest temperature possible for any given conditions. I

It is desired to maintain a maximum concentration of the hygroscopicsolution for any temperature to create a maximum drying effect. However,an increased concentration raises the freezing temperature of thesolutionand vice versa. Also, for a given concentration, a'temperaturedrop due to cooler sea water being encountered may freeze or crystallizethe solution. This may be overcome by maintaining the solution at adiluted concentration such that the freezing point will be below thetemperature of the coolest sea Water to be passed through. The dryingetfectiveness of the solution will then be greatly decreased for highertemperatures, however.

With organic hygroscopic solutions'such as the glycols, a'similarproblem appears due to solution thickening at very low temperatures andincreased carry-out at higher temperatures for concentrated solutions.

To overcome this dilemma, the concentration of the hygroscopic saltsolutionis maintained at maximum con: centration for any sea watertemperature, and this concentration decreases for lower temperatures. Inaccomplishing this, two upright, parallel columns 34 and 35 areemployed. Column 34 is filled with a given amount of reference liquid sothat the top of it will be at the bottom of plug 36 for the coolesttemperatures to which the liquid may be subjected. Plug 36 is'attachedto the top of tube 34 by athreaded shank 37 which provides an adjustmentfor the height of the plug. Two tubes are necessary in marineapplications to overcome the roll'of the ship whichsimilarly affects thepressure in each tube and thus nullifies the effect of the rolling.

A cooling jacket-38 surrounds tube 34 through which the hygroscopicsolution is passed which is supplied from spray bar 20 or 24 or someother part ofthe washer-- generator unit through a reservoir. Thesolution then passes throughtube 35 bymeans of pipe 40 and overflows thetop of tube 35, into chamber 41, and back to the unit by means of pipe42.

To assure aconstant flow through jacket 38 and tube 35, a reservoirmaybe employed. This consists of an outer receptacle 53, an innerreceptacle 54, a drain pipe 55 which leads back to the sump 13, or someother part of the unit, a supply line 56, and an exit line 57 with hole58 that connects to the cooling jacket 38. The hygroscopic solution issupplied to the inner receptacle 54 from supply line 56. A portion ofthe solution enters hole 58 and flows by gravity to jacket 38. Theremaining fluid overflows inner receptacle 54 into outer receptacle 53and, hence, to drain pipe 55. A constant head is thus maintained betweenhole 58 and the top of height of the reference liquid also varies withthe tempera ture.- Plug 36 is employed to amplify the height dilfer enceand accordingly vary the pressure in the tube. The

pressures in the two tubes are measured by -a difierential pressuretransmitter 43'which is commercially available.

It senses pressure in corresponding portions 'of tubes 34 and 35 throughpipes 39 and; 49. This instrument is set for a pre-determined pressuredifierential between the two tubes. Air is supplied to the instrumentthrough line 44 and pressure is maintained in outlet line 45 accordingto .the actual temperature difierential' in comparison to the setdifferential. The pressure in line 45 controls the outlet pressure inline 46 leading from a pressure controller 47 which is likewisecomniercially available; Air to this is supplied through a line 48. Line46 is connected to pneumatic valve 33 whose degree of opening isdetermined bythe pressure in this line.

In operation, a portion of the hygroscopic solution, which is near thetemperature of the sea water in coil 15, is slowly passed through jacket38 and tube 35. If the sea water becomes warmer, for example, thehygroscopic solution and the contents of the two tubes 34 and 35accordingly rise in temperature, thus changing their densities. Thereference liquid level also rises and this rise is accelerated by theplug 36. The resulting increased pressure in this tube over an'dabovethatin tube 35 causes differential pressure transmitter 43 to increasethe pressure to controller 47 which increases the pressure to pneumaticvalve 33. This is further opened allowing a greater quantity of theheating medium to' pass through the coil 28 and concentrate the solutionto a greater extent. If the sea water temperature becomes cooler, theopposite occurs.

Tube 34 is provided with expansion chamber 50 to limit the maximumheight to which the reference liquid may rise. This limits the maximumconcentration of the solution to any pre-determined amount and is asimple, effective way to limit the degree of concentration so that thesolution will not salt out when shut down and allowed to cool in a coldenvironment.

Plug 36 may comprise an unlimited number of configurations, an exampleof which is illustrated in Figure 2'. Here, the plug is larger indiameter near the bottom 51 than at the top 52. During expansion due toheat, the liquid rises faster at lowerternperatures and slows when theliquid level reaches portion 52. Thus the concentration is likewiseincreased faster at low temperature changes and slows at higher ones.The shape of the plug can be fitted to any rate of change ofconcentration desired according to the various conditions encountered inthe specific situation.

Another form of the controls is schematically illustrated in Figure 3.In this form, two similar tubes 34 and 35 are employed with similarsupply line 57, cooling jacket 38, line 40, drain pipe 42, and expansionchambers 41 and 50. Air is supplied at constant pressure to lines 61 and62. This air is initially adjusted by means of flow meters 63 and 64 toobtain constant flow in eachof air pipes 65 and extending to thebottomportions of tubes 34 and 35. The pressure in that portion of theair pipes above the tubes is received by a difierential pressureinstrument 67 which maintains a given pressure difierence between thetwopipes by controlling the regenerator valve and thus change solutionconcentration. A thermostatic instrument 68 measures the temperature ofthe sea water or hygroscopic solution'by means of a bulb 70. Thisinstrument 68 thenresets the pressure diflerence to be maintained byinstrument 67 according to the temperature of the sea Water orhygroscopic solution. Instrument 67'has air supplied to it from a line71 and controls the outlet in. line 72 according to the pressurediflierential. Line- 72 leads directly, in this case, to pneumaticallycontrolled valve 33;

In operation, the reference liquid: in tube 314' ismaintained atwasubstantially constant. level by means of expansion chamber 50' and thesolution level: in tube 35 is maintained constant byoverflbw chamber 41.The only change in the heads of these liquids is now eiiected by densitychange due to temperature change. As density increases the headsincrease and pressure inair pipes 65 and 66 likewise rises. Thedensitiesin both tubes are not similarly afiected and the pressures ofthe air pipe consequently do not. similarly change; The resultant newdifferential between the pressures is responded to by instrument 67 andthus changes air pressure in line 72 which further opens or closes valve33.

As previously mentioned, the difierential control pressure setting ininstrument 67 is changed by thermostatic instrument 68 as thetemperature changes. The setting of valve 33 is consequently changed tomaintain maximum concentration of the hygroscopic solution for any giventemperature. In eliect, temperature change is accounted for in theapparatus of Figure l by the height change of the reference liquid andis accounted for in the apparatus of Figure 3 by the thermostaticinstrument that changes the control setting of the differential pressureinstrument.

Further modifications will be apparent to the reader, such as using seawater in cooling jacket around both tubes to produce temperature change.Many modifications may be made Without departing from scope of ourinvention or the teachings contained herein.

We claim:

1. Dehumidifying apparatus comprising, in combination: wall meansforming, a contact chamber for contacting air to be dehumidified withhygroscopic solution; duct means for passing air to be dehumidifiedthrough said chamber; contactor means comprising solution deliverynozzles for contacting air passing. through said chamber withhygroscopic solution; a source of coolant fluid; means for transferringheat from said solution to said coolant fluid whereby to cool saidsolution for contact with air to be dehumidified; regenerating means forremoving water from solution; first control means for controlling theoperation of said regenerating means to maintain the concentration ofsaid solution substantially constant; and second control means aflectedby the coolant fluid temperature for adjusting the operation of thefirst control means in a manner to maintain said concentrationrelatively higher when said coolant fluid is relatively warmer.

2'. Dehnmidifying apparatus for ships comprising, in combination: wallmeans forming a contactor chamber for contacting air to be dehumidifiedwith hygroscopic solution; duct means forpassing air to be dehumidifiedthrough said chamber; an internally cooled heat exchanger disposed insaid chamber in the path of said air; sea water duct means forcontinuously passing sea Water through said heat exchanged to maintainthe same substantially at sea water temperature; circulating means forcirculating a streamof hygroscopic solution through said chamber andover said heat exchanger in contact with said air; a regenerator forremoving excess water from the hygroscopic solution; means forcirculating solution from said stream through said regenerator and backto said stream; control means responsive to concentration of thehygroscopic solution and to changes in sea water temperature; andadjusting means for adjusting the operation of said regeneratorresponsive to said control means to maintain a substantially constantconcentration of solution at substantially constant sea watertemperature, and to maintain a less concentrated solution at colder seaI Water temperatures.

3. Dehumidifying apparatus comprising in combination: a contactor unithaving a first casing, a cooling coil within said first casing throughwhich a cooling medium of varying temperature is passed at a constantrate of flow, first spray means for spraying hygroscopic solution oversaid coil, first duct means for carrying air to be dehumidified to oneportion of said first casing; second duct means for carrying air fromanother portion of said first casing to the conditioned space andarranged to allow air from said first duct means topass by said coilbefore entering said second duct means, first blower means formaintaining air flow from said conditioned space through the first andsecond duct means, and a first drain pipe connecting the bottom of saidfirst casing to a sump; a regenerator unit having a second casing, aheating coil within said second casing through which a heating me diumis passed, valve means for controlling the rate of flow of said heatingmedium through said heating coil, second spray means for sprayinghygroscopic solution over said heating coil, third duct means forcarrying air from an outside space to one portion of said second casing,fourth duct means for carrying air from another portion of said secondcasing to the outside space and arranged to allow air from said thirdduct means to pass by said heating coil before entering said fourth ductmeans, second blower means for maintaining a flow of air from saidoutside space through the third and fourth duct means, and a seconddrain pipe connecting the bottom of said second casing to a sump;hygroscopic solution; and control means for controlling said valvemeans, including: a first upright tube containing reference liquid; asecond upright tube; a cooling jacket around said first upright tube; anoverflow chamber at the top of said second tube; pipe means for carryinghygroscopic solution through said cooling jacket, second tube, andoverflow chamber; a plug in said first tube located adjacent the levelof said reference liquid contained therein; a differential pressuretransmitter operatively connected to corresponding portions of the firstand second tubes; and means for controlling said valve means in responseto said difierential pressure transmitter.

4. Apparatus according to claim 3 in which said plug is connected to thetop of said first tube by means of a threaded shank whereby said plugmay be vertically adjusted.

5. Apparatus according to claim 3 in which said plug may be ofnon-cylindrical contour to vary the amount of change in height of saidreference liquid in response to a given change in temperature of saidcooling medium.

6. Dehumidifying apparatus comprising in combination: a contactor unithaving a first casing, a cooling coil within said first casing throughwhich a cooling medium of varying temperature is passed at a constantrate of flow, first spray means for spraying hygroscopic solution oversaid coil, first duct means for carrying air to be dehumidified to oneportion of said first casing; second duct means for carrying air fromanother portion of said first casing to the conditioned space andarranged to allow air from said first duct means to pass by said coilbefore entering said second duct means; first blower means formaintaining air flow from said conditioned space through the first andsecond duct means, and a first drain pipe connecting the bottom of saidfirst casing to a sump; a regenerator unit having a second casing, aheating coil within said second casing through which a heating medium ispassed, valve means for controlling the rate of flow of said heatingmedium through said heating coil, second spray means for sprayinghygroscopic solution over said heating coil, third duct means forcarrying air from an outside space to one portion of said second casing,fourth duct means for carrying air from another portion of said secondcasing to the outside space and arranged to allow air from said thirdduct means to pass by said heating coil before entering said fourth ductmeans, second blower means for maintaining a flow of air from saidoutside space through the third and fourth duct means, and a seconddrain pipe connecting the bottom of said second casing to a sump;hygroscopic solution in said apparatus; and control means forcontrolling said valve means, including: first upright tube containingreference liquid; a second upright tube; a cooling jacket around saidfirst upright tube; an overflow chamber at the top of said second tube;pipe means for carrying hygroscopic solution through said coolingjacket, second tube, and overflow chamber; a pressure responsive devicefor measuring the pressure differential between corresponding points ofsaid tubes; and means for controlling said valve means in response tothe measured pressure differential whereby said valve means tends to bemore fully opened when said differential increases and tends to be morefully closed when said differential decreases.

References Cited in the file of this patent UNITED STATES PATENTS

